A Kampo extract powder (hereinafter, occasionally referred to as “extract powder”) is obtained by extracting a Kampo formula with an aqueous solvent followed by concentration and drying. Therefore, in general, the powder is highly hygroscopic and is thereby desired to be prepared by a process not requiring the addition of water. Such a preparation process is also preferred because it allows omission of the granulation step and ensures stability for those that are unstable to water.
Accordingly, employed are a direct tableting method where tablets are prepared by direct compression of a powder mixture of a tablet composition containing an extract powder and a dry tableting method (slug method) where tablets are prepared by forming a granulated substance having a small diameter and containing an extract powder and tableting a powder mixture of a tablet composition containing the granulated substance.
However, such Kampo extract-containing tablets produced by these tableting methods have a long disintegration time, which cannot be sufficiently improved only by adding a general disintegrant, and have low dissolution properties. Thus, satisfactory tablets have not been prepared.
In order to solve this problem, some methods have been tried. For example, the content of an extract powder in a tablet is decreased, or a large amount of a diluent, a disintegrant, a binder, or other excipients are added to a tablet. However, these methods cause problems, for example, an increase in dose of tablets, an increase in tablet size, and an increase in manufacturing cost due to the expensive disintegrant. Furthermore, a tablet of which dissolution properties are improved by adding sodium hydrogen carbonate is also known, but it is not imparted with sufficient advantageous effect.
In addition, if a composition contains a large amount of sodium hydrogen carbonate, it is concerned that the alkalinity of the sodium hydrogen carbonate may affect the stability of the extract powder.
As a technology for solving the above-mentioned problems and improving the disintegration and dissolution properties of tablets containing a Kampo extract powder, the present applicant has already proposed a tablet composition containing Kampo extract that contains a Kampo extract powder, cellulose glycolic acid, and sodium hydrogen carbonate (Patent Document 1).
Patent Document 1: International Patent Publication No. WO2004/006945 (for example, Claims)